As an infrared sensor, a pyroelectric infrared sensor using a pyroelectric effect, a resistance variable infrared sensor using a temperature change rate of resistance in which a material has, an junction infrared sensor using a change in electrical characteristics of a semiconductor pn junction or the like are known. Especially the pyroelectric and the resistance variable infrared sensor that can operate at a normal temperature are used for fire detection or human body detection. Further, these infrared sensors have an advantage that the infrared spatial distribution can be easily imaged in high resolution by placing infrared detection elements in an array, and they are used for security in a dark place and flaw detection in the structural material or the like.
On the other hand, by advance in information communication technology in recent years and expansion of network infrastructure, there is a movement of using a new sensor such as energy-saving of building air-conditioning, and a small-sized sensor device with a low manufacturing cost is desired to realize the system that uses many sensors at the same time.
A basic configuration of the pyroelectric infrared sensor array is explained with reference to FIGS. 7A and 7B. FIG. 7A is a cross-sectional diagram showing the configuration of the pyroelectric infrared sensor array. FIG. 7B is a perspective view showing the configuration of the pyroelectric infrared sensor array. As shown in FIG. 7A, the pyroelectric infrared sensor array is composed of an infrared detection element 101, a substrate 102, an optical diffraction lens 103, and an optical filter 104. The infrared detection element 101 is composed of pyroelectric ceramic and a single crystal including a pyroelectric effect. The substrate 102 is composed, of a silicon substrate or a glass substrate.
An array of the infrared detection elements 101 is formed and integrally bonded by the film deposition process or attachment to the substrate 102, and sealed through formation of electrodes and wires for electric connections. The optical filter 104 which transmits only the infrared rays of a wavelength suitable for a detecting object is provided in the sealed package. Moreover, the optical diffraction lens 103 such as a Fresnel lens is used to ensure a wide viewing angle, and a wide viewing angle is realized (see PTL 1). Infrared distribution in the space is converted into electrical signals as a polarization state change of the array of the infrared detection elements 101 surface, and is output as image information through a signal amplifying circuit and a digital processing circuit (see PTL 2).
Further, in the pyroelectric infrared sensor, in order to realize a wide viewing angle without using an optical diffraction element such as a lens, PTL 3 discloses a technique for processing a pyroelectric member and using a plurality of curved surfaces or planar surfaces as a light-receiving surface. Furthermore, PTL 4 discloses a technique for providing a plurality of sensors in an array over a flexible substrate and using it as a radiation imaging element.